If Only You Had Listened
by NightwingNinja17
Summary: The enemy of my enemy is my friend as the old quote goes. But what if the enemy decides to attempted to eradicate you. What would you do and how would you survive? Live the tail of suspense as someone sneaks aboard the UNSC Infinity and targets someone on board. Will they be able to capture him before it's too late and damage is done? Halo AU.
1. Chapter 1

**Hey guy! I'm back with a new story! This story is based on characters from the Halo video game franchise. I have two personal favorite characters at the moment. The first one of course being Master Chief. I love his personality and how he doesn't let anyone get in his way of his missions. My second favorite character is Thomas Lasky. At the moment, I couldn't tell you why I like him as a character, but I hope to figure that out soon.**

 **I know some of you guys who are Halo fanatics will catch this so I** **'m going to say this ahead of time. For the sake of this story, I'm going to say that Lasky's older brother Cadmon isn't dead. For those of you who aren't Halo fanatics, Thomas Lasky has an older brother (seen in Halo: Forward Unto Dawn) named Cadmon who was an ODST before the Covenant started attacking. Well in Forward Unto Dawn, it is mentioned that Cadmon was killed in the line of duty. But for this story, I'm going to pretend that didn't happen**

 **I also won** **'t be keeping exactly to the canon, but I'm going to try and stick with it as much as possible..**

 **Anyway, let** **'s get on with the story.**

 **Prologue: The Arrival**

A lone figure walked into a shop on the square in Argon, a newly established human colony on earth. This particular shop carried anything you can imagine that was used in the medical field as well as pest control..

 _"So what can you tell me about your brother?" a female voice asked a man, no, a soldier who stood directly in front of her._

 _"_ _What do you want to know sir?" the man asked._

He walked in kind of slowly as if he was expecting someone to stop him en-route. He scanned his surroundings before walking up to the cashier.

 _"I want to know everything, from what you knew of him when he was younger and what you know of him now."_

"What can I help you with?" The man behind the counter questioned.

But the lone figure didn't answer. Instead he pulled out a gun and pointed it towards the shop keeper.

 _"Sir, I haven't been in contact with my brother since my supposed death," he explained to the woman._

"Hand me all of that," the figure exclaimed as he pointed towards containers that held a milky looking substance inside.

 _"I know, that's why I want to know everything that you_ do _know about him. Start from when he was a cadet."_

The cashier just stood there for a few seconds, staring at the gun in the process.

"Now!" the man exclaimed as he tightened his grip on the trigger.

 _"I also don't know much about that, sir. All I know is that his friends called him an innie-sympathizer back during the human insurrectionist war. He never really went into details in the messages we sent back and forth." the man continued to explain to his superior._

The cashier hurried to grab the items in question and gave them to his assailant.

The figure smiled in an evil manner and proceeded to put the small vials in a briefcase that he held in his hand.

 _"Did, you know that he has an allergy to cytoprethaline?" the woman asked the soldier as she checked a data pad that was sitting on the desk in front of her? She looked at the man and gave him a look of accomplishment._

 _"_ _No sir, I didn't know that. As I previously stated, I lost contact with him after I pretended to die."_

 _"_ _It's said that only 1 in 50,000 people have an allergic reaction to it."_

 _"_ _You mean that my brother can't do cryo sleep?" he asked._

The shopkeeper got one quick glance at the contents inside and saw a pre-measured self-injector and the vials hidden away beneath the foam covered insides.

 _"No comment and I have no further questions at this time. You are dismissed_

The man behind the counter gave the figure a strange look before he closed the brief case and left.

 **Captain Thomas Lasky's POV**

 **One day later….**

It had been a grueling year since I became Captain of the biggest ship the UNSC had created. Many things happened from the time where _Infinity_ got sucked into Requiem's gravity field to when me and my crew helped rescue Master Chief from the wreckage of the Diadact's ship.

The Master Chief and I have grown to be good friends as the Spartan tends to stay aboard my ship more times than not. In fact the Spartan was who I was expecting aboard here soon.

He was returning from one of the many missions he has been sent on since his return. Many of the high ranking UNSC officials were very excited to hear the news. But with it came very enthusiastic officials who were, in my opinion, way to eager to put the Master Chief back to work.

I stood in the lower hangar bays of _Infinity_ waiting for my friend to arrive. I was surrounded by four young marines assigned to protect me from anyone or anything. They stood looking around the hanger as if they had never been in one before.

I overheard the young soldier at the hangar command post question an incoming ship for its credentials.

"Sir, an incoming Pelican requests your permission to land," the young hand explained,"They say Sierra-117 is on board."

"Let them through," I ordered.

She relayed confirmation to the the ship as the hanger bay doors began to slowly open revealing an awaiting Pelican drop ship on the other side. Once the doors were fully open the pilot of the ship carefully maneuvered the ship into position and set it down. The back cargo hold door to the Pelican began to lower.

Then out walked the man of the hour Master Chief followed closely by several other Spartans, Marine soldiers and Marine Cadets. They all approached me and once they were close enough saluted me.

"At ease gentlemen," I said and watched all of them relax. I could see physical exhaustion written all over the marines faces. I kind of chuckled to myself as I thought that the marines probably weren't able to keep up with the Spartans' pace, "Go to your quarters and rest. I want a debrief at oh-15:00"

Everyone except for Master Chief left.

"I hope everything went well with the cadets. I know how much of a hassle they can be at times," I questioned my friend.

"They performed their part, but they don't match up to a Spartan," he replied. I had to chuckle at this for he was right. Marines were good in their own right, but not as good as a Spartan and since he had been tasked with training this group of cadets, he had a lot on his hands.

"Well you go rest and I expect a debrief from you on the ways we can make those marines better," I replied as I lightly patted the Chief on the shoulder.

He answered with a slight nod and then turned to head toward the exit.

I looked back towards the Pelican everyone just stepped off of and noticed a figure just standing in the doorway looking straight at me. The presence of this man made the hairs on the back of my neck stand on edge. His face was obscured by the helmet the pilots wore so I couldn't get a good look at his face. So I opted to keep an eye out for this guy in the future.


	2. Chapter 2

**Chapter 1: All in a Day's Work**

 **3rd Person POV**

The lone figure waited for everyone aboard the Pelican to leave before heading back to the cockpit. He had succeeded in incapacitating the original pilot and was excited to get behind enemy lines.

He then fiddled with the controls of the small aircraft as he encrypted a communication to someone. Once he finished with the encryption, he contacted someone.

"Admiral, I'm aboard _Infinity_ ," he explained to the unknown officer on the other side.

" _Good. Does he suspect you?"_ a female voice exclaimed.

"I don't believe so," I replied.

" _Then you know what to do._ "

The communication promptly ended and the man left the cockpit of the Pelican. His briefcase shrunk down to a manageable size that fit directly underneath the vest of his uniform without looking too conspicuous.

" _I need to locate the medical wing,"_ he thought to himself before making his way out of the hanger.

 **Master Chief's POV**

It was home to me. The Infinity became my home after the crew rescued me in when I floated around in the wreckage of the Diadact's ship. Of course when the news spread that I was alive, I didn't stay idle for long.

But I was thankful that they gave me sometime to mourn for my fallen friend Cortana.

It was strange not to hear her voice inside of my head either joking around or telling me my next move. I miss that and it made my heart ache and long for her voice just to cut through the silence.

I jumped slightly when I heard a knock at the door to my quarters.

"Come in," I curtly replied.

The door swung open and in walked a young female Spartan I have come to know. Her name was Jade and she had taken a liking to my work ever since we met. She was a Spartan IV, the bunch that almost didn't qualify as Spartans. Jade was the exception to that rule as she rose through the ranks to become the leader of Fireteam Wolfpack, one of the newest Spartan IV fireteams. She valued my advice as she told me earlier that she had always admired me from the time she was fully able to process what all was going on. She was wearing the traditional under armor that all Spartans seemed to wear when the armor wasn't on. Her black pixie cut hair was brushed ever so neatly on top of her head.

"So how was the mission?" She questioned me with her thick Irish accent from Earth's colony of Dublin.

"It was interesting, if you count the fact that the marines were afraid of their surroundings more than they were the enemy," I explained to her.

"Yeah that sounds like most marines I know," Jade replied.

"You're going to have to go to the debrief Captain Lasky if you want the details," I replied.

Her face lit up as she stood.

"I'd like that," she replied smiling.

"Oh, am I interrupting anything?" The voice of the ship's AI echoed through my room.

"No Roland, you aren't interrupting anything," I reassured him.

"Well then, Captain Lasky is ready for the debrief," he explained to me.

"Thanks Roland, tell him I will be there shortly."

 **Lone figure's POV**

I had been watching my target ever since the Pelican landed on board _Infinity_. But he seemed to be onto me. Every so often I would see him look in my direction with a concerned look on his face. I wouldn't blame him. He needs to watching back.

I was slightly taken aback when two Spartans, one a female the other a male, walked into the room, taking my target's attention elsewhere besides me. This mad me happy. I then turned back towards the medical wing and waiting for my turn to strike.

 **Captain Lasky's POV**

"Thanks for that intel Master Chief. I will definitely look to have the marines trained like you suggest," I replied at the end of the Chief's debrief.

"Your welcome, sir," he replied.

"Okay I have to ask you this question," I began, "Did you know everyone who was aboard the Pelican with you?"

"Yes sir. Why do you ask?"

"I saw a man just standing on the back door looking straight at me when all of you guys had left and now I can't shake the feeling that I am being watched," I replied.

Master Chief just stood there in silence. The orange reflection of his helmet didn't stop me from feeling that he was deep in thought.

"Now that you mention it, the pilot seemed strangely quiet. Normally the Pelican pilots are a lot more talkative than this guy was," the spartan explained.

"Do you need some added protection?" Jade, my other spartan friend, asked me.

"That won't be necessary but if things do get worse I'll let you know," I stated.

"I will keep watch out for this guy too. If he decides to rear his face against you, I will be able to stop him."

"Thanks Chief. You are dismissed."

He nodded his head and left with Jade, the female spartan that had walked in with him.

I was tired from the long day that I had so I let Roland know that I was headed back to my quarters to try and get some rest.

But as I walked the massive hallways of _Infinity,_ the feeling that I was being watched grew. I didn't know who or where it was coming from, but I felt my senses become more aware.

I was startled out of my thoughts though when someone taller then myself grabbed me, wrapping his arms around my shoulders, impairing my forward motion. I tried to fight my way out of his grasp, but found it to be near impossible as his strong forearms squeezed tighter.

"Don't make a sound or else things will be worse for you," the person explained to me as he pointed a Magnum at my head.

He then dragged me into an abandoned room that I didn't know existed and pushed me hard against some crates that filled the room, freeing me from his grasp. I say up and tried to stand up, but found a sheering pain spread across my leg, its source was located around my ankle.

Once he holstered his weapon, he fiddled with something out of my line of sight and then turned back towards me with something in his hand.

I immediately recognized it as a pre-measured self-injector. The only time I'd seen one used was when a doctor was injecting cytoprethaline before being subjected to cryo sleep.

Not knowing what was inside the injection device, I panicked and attempted to run out the same door that I came in, but my abductor was faster then I was. He managed to catch me, this time wrapping his arm around my neck, stopping me in my tracks.

"Before I inject this into you, you should know that the substance will knock you unconscious and you won't remember a thing about this encounter," the man whispered into my right ear. I tried to struggle out of his grip, but it wasn't budging.

I then felt a sharp pain in the side of my neck and then felt a cool sensation run through my body. This stopped me dead in my tracks. It seemed to take a while before the man completed the task which made me wonder how much of the stuff was inside.

The man then guided me towards the door of the room. But as I walked, I began feeling weak and light headed. I tried shaking to off, but found that in doing so, it made the symptoms worse.

I finally made it to the door and that's where the man let me go. I quickly opened it, eager to leave the presence of that creepy man, and walked out into the bustling hallway.

But then dizziness set it as well as a strange ringing in my ears. I felt so confused and lost in my own ship.

I started getting tunnel vision and then soon found my legs giving out from underneath me, to where one miss step could hurt me drastically.

I was almost to my quarters when my legs finally did give out and I collapsed to the ground. I could see three marines hovering over me asking me questions that I could no longer hear.

Finally I closed my eyes and succumbed to the feeling and fell unconscious.


	3. Chapter 3

**I am so sorry this took so long to post! I have a bunch of the chapters pre-written so hopefully at somepoint they will all be posted here. Keep on the lookout! :D**

 **Chapter 2: What Just Happened?**

 **Lasky's POV**

"Captain can you hear me?" I heard a voice call out to me. It was slightly muffled due to a constant ringing in my ears.

" _What happened?_ " I thought to myself as I raised my hands to cover my face. I then opened my eyes to find a small, bright light shining down into them. I quickly shut them again to avoid the pain and to let my eyes adjust to the light. I then sleepily re-opened them again to discover that I was laying down in the infirmary.

"What happened?" I finally voiced my question sounding sluggish and pained all at the same time. I drew my hands down across my face to try and shake the tired feeling off.

"We don't know, you just collapsed," the voice that I now recognized to be Dr. Jameson Williams, "We found traces of Sevoflurane which is what knocked you out and another substance we have yet to identify. The strange thing is that the drug usually only works when it's inhaled."

He wrote something down on a piece of paper that was sitting in front of him and then looked back to me.

"Do you remember anything about what happened?" he continued to question me, changing the subject.

I thought hard, trying to remember the moments before I woke up, but found the memories to be non-existent. The doctor must have clued in on this as he patted my shoulder.

I took a deep and ragged breath. It felt like I had just been scared. I stared up at the ceiling in deep thought. How could I have forgotten such a traumatic event?

"How long was I out?" I asked Jameson.

"Four hours," a new voice explained, "Spartan Jade was the one who found you."

I made a mental note to thank the young spartan personally.

I shakily propped myself up on my elbows to find Commander Palmer sitting in a nearby chair looking extremely worried. The doctor the helped me to sit up fully and then I swung my legs of the side of the bed.

"Take it easy, sir" Dr. Williams instructed me as he grabbed my my wrist as I grabbed his and pulled he me to my feet. He didn't let go until he was sure I wouldn't collapse upon the sudden disappearance of a support. Once he did however, I stood staring at the ground for a few seconds before raising my head to meet the gaze of my friends.

They watched me with keen gaze for a few seconds probably determining whether or not to allow me to leave. I felt honestly fine except for I felt slightly groggy and had a small headache.

"You take it easy now," the doctor warned, "If any of the symptoms come back, come straight here."

"I will," I replied softly, "Thanks."

"You're welcome, sir," he replied.

 **Master Chief's POV**

I had just finished pitting the first set of Marine Cadets against the Spartan war games when Captain Lasky joined me in the training room. Once glance at him told me that he wasn't doing well at all, but wasn't letting that get in the way.

"Are you alright, sir?" I questioned my superior officer.

"Been better," he replied as he gazed across the massive training room he looked at me once and even though he couldn't see my face, he knew that I wasn't totally convinced, "But I'm fine. How are they doing?"

"The sergeant is getting no where with them," I replied, "They seem to be too fascinated with the technology of the training yard then really taking it seriously."

I began to walk towards the entrance to the training yard.

"What are you going to do, sir?" I asked the captain.

"I'm going to go join them. Perhaps if they see someone in command do it, maybe it will knock some sense into those hard heads of theirs."

 **Lasky's POV**

It was strange walking into the training room. I hadn't been in or on a training field like this one since I was a cadet at Corbulo Academy of Military Science. Everyone's eyes turned toward me making me feel a little bit uncomfortable. The sergeant let me have the floor as I explained to him my goal.

"Gentlemen, I've been watching you for sometime now and I've been told that you haven't been listening to Sergeant Gordon. I also have received word from Spartan 117, that you guys got a little star struck in our real field. I know where you've been but now isn't the time to slack in your duties. So during the next exercise, I'll be joining you."

The cadets' chatter picked up. I could tell that they were surprised that I was joining them. Most of them were no older than sixteen years of age, with some of the youngest being 14. I could see the fascination in their eyes as they looked between me and the training yard that surrounded them.

"Why do you want to join us?" someone from the crowd of cadets asked me.

"I was a cadet like you guys not long ago and know what it's like not to want to follow orders. But I finally had to step and become a leader when the academy I was training at was attacked by the Covenant. If it wasn't for the fact that I began to listen to orders, I wouldn't be here standing in front of you today," I glanced up at Master Chief as I remembered being rescued by the Spartan

This seemed to catch the cadets' attention as they all began to whisper and talk amongst themselves. But everything went silent as the Sergeant walked up.

"This next exercise, will be simulating what it will be like coming out of a cryo tube like ODSTs do," The sergeant explained, "Since Captain Lasky is joining you guys, he will take point. If you disobey his orders, then I will make sure that you will get the worst position during the rest of the training year. Am I understood?"

They all responded with simultaneous yes, sirs and then filed out to go get ready for the exercise.

"Come with me and I can help you find the equipment you need," he explained as he guided me out of the main floor.

"Thanks," I replied following him closely.

This time I wasn't as concerned about the marines not following orders as I was my reaction to the cytoprethaline. It had been a long time since I had to worry about my allergy as we rarely went into cryo sleep anymore. But with what happened earlier, it became a concern.

But I wasn't about to let it stop me from helping out the people that I cared so much about.

 **Master Chief's POV Fifteen minutes later...**

I observed from a distance as the simulation started. It seemed to being going better this time since Lasky stepped in to assist.

I picked Lasky out from the large group of soldiers rather easy. His armor was a difference color then that of the other marines. It was strange seeming him in gear very reminiscent of ODST armor. It reminded me of the time I saved him and two of his fellow cadets on Cirnicus IV.

I could tell something was wrong though as he usually lagged behind just a bit anything they were running to places. I didn't know what would cause that if he wasn't doing it on purpose.

"Master Chief!" I heard someone call my name in an urgent manner.

"Dr. Williams," I said as I nodded my head to acknowledge his presence.

"Where's the captain?" He asked me. He sounded desperate about something that I couldn't make out.

I pointed to the training room.

"He's in there training with the Cadets," I told the doctor.

"What simulation are they running?" He continued to inquire of me.

"I don't know the full nature of the exercise but it's got something to do with ODSTs."

"Did they come out of cryo tubes?"

"Yes they did," I replied, "Why is this important?"

The doctor took himself sometime to compose himself before giving me the details.

"Did you hear what happened to him earlier?"

I shook my head no.

"He passed out for no reason in one of the hallways. Spartan Jade was the one that found him," he began, "I ran some tests to see what was going on, and found traces of Sevoflurane and an unknown chemical that I was unable to identify at the time. I just now figured out that the unknown chemical was an extremely high dose of cytoprethaline."

"Why is cytoprethaline significant?" I asked.

"He's highly allergic to the drug," The doctor finally filled me in, "And if they did a cryo-tube ejection, then he has been injected with more than his body can handle."

I looked back towards the scene and it all began to make sense. He wasn't lagging behind for no reason, he was in pain.

"We need to get him out of there now otherwise, he is in big trouble."


End file.
